Refit MS JAROTOA - Electrodacus BMS and Victron components

[Tom Kühne]

Hello from Switzerland,

I am planning to upgrade to lithium batteries

The big question with charging is charging from the alternator in order to be able to charge with as much amperes as possible.

What about the layout!

Suggestions for improvement!

Can the Victron Energy BMS 12-100 be used to function nr as a B to B converter and to limit the charging strength by means of the inserted fuse.

The BMS function is made by the SBMS0

Is 1 DSSR20 correct for 4 55W solar panels (all connected in parallel)?

The line is approx. 8 meters long and the cable size is 6mm2

or do several DSSR20 have to be used?

Operation only on weekends from April to September.

No shore connection available in the port, only charging with 210W solar planel and alternator.

The engine running time is approx. 0.5h to 2.0h per day.

The Blue Smart charger can only be used every 4 weeks for a few hours in a port with a shore connection.

Thank you very much and greetings from Switzerland on Lake Zurich



Bigger picture resolution here:

https://drive.google.com/file/d/1_T_WBlrsV6Qrp75koXk9g2jSsmEDv-3T/view?usp=sharing

[Oberon Robinson]

Hi Tom, your circuit diagram came through super tiny, can you post a larger version?

Most people use something like a Victron Orion-TR or a Stirling B2B to charge lithium from an alternator.  Looks like you maybe have a smart alternator regulator in your diagram?  You have to be careful with alternator charging because a lithium battery will take a huge current and burn up your alternator in no time if you don't regulate it.

On Sunday, 14 March 2021 at 11:57:38 UTC-4 Tom Kühne wrote:

Hello from Switzerland,

I am planning to upgrade to lithium batteries

The big question with charging is charging from the alternator in order to be able to charge with as much amperes as possible.

What about the layout!

Suggestions for improvement!

Can the Victron Energy BMS 12-100 be used to function nr as a B to B converter and to limit the charging strength by means of the inserted fuse.

The BMS function is made by the SBMS0

Is 1 DSSR20 correct for 4 55W solar panels (all connected in parallel)?

The line is approx. 8 meters long and the cable size is 6mm2

or do several DSSR20 have to be used?

Operation only on weekends from April to September.

No shore connection available in the port, only charging with 210W solar planel and alternator.

The engine running time is approx. 0.5h to 2.0h per day.

The Blue Smart charger can only be used every 4 weeks for a few hours in a port with a shore connection.

Thank you very much and greetings from Switzerland on Lake Zurich

https://drive.google.com/file/d/1e1sWBvMA7_-7socA9fL_I5NtDiU7mqEe/view?usp=sharing

[Oberon Robinson]

Never mind about the image size, I didn't see your Google Drive link at first!

[Tom Kühne]

Hi Oberon,
I know Orion-TR and sterling B2B  but they make only 30A
i want a little more like up to 50A!
Without burning the Alternator.

Has anyone had experience with the Victron BMS, to use it only as a limiter to limit the current.

It should be possible to change this by means of the fuse used.

Thus the maximum temperature of the alternator could be determined.

[Dacian Todea]

You can use two B2B in parallel to get higher current but Renogy has 20,40 and 60A B2B chargers the problem may be your alternator not being capable to deliver that much current and get damaged if you push that to far.

There is a reason most B2B chargers are in the 20 to 40A range ans most alternators can not handle more than that continually.  For each kWh you get out of the alternator you will be using a liter of fuel so charging from alternator is also incredibly expensive and should be avoided as much as possible as is 50x more expensive than solar PV charging and maybe around 5 to 10x more expensive than charging from grid.

The 55W panels have probably a max current of 6 to 7A and a fuse rating of probably 15A thus only 3 of them can be paralleled without using individual panels fuses so you can connect 3 of them to the DSSR20.

I can not see your diagram.

[Tom Kühne]

Hi Dacian,

The drawing is now updated

The 4 Panel are connected in parallel Kabel 2.5mm2, lenght +-1meter to the conncetor box.
Then with one cable 6mm2 to the bus bar lenght +- 8 meter

Each panel provide 3 Amp.   in total 12 Amp.

The maximum I measured in full sun and half empty lead acid batteries was 10 amps.

Can these 4 panels with 210 watts be operated with a DSSR20? Otherwise I would have to install a second cable, which is difficult and I definitely want to avoid it.

Can the DSSR20 switch these 10 amps (a maximum of 12 amps according to the data sheet)?

Data 55W Module:

BP SOLAR

TYPE BP 555/2

Peak Power P max: 55.0W

Peak Power Voltage Vmp: 18.0V

Peak Power Current IMP: 3.0A

Short circuit current Isc: 3.2A

Open Circuit Volatge: 22.0V

Minimum Peak Power P min: 50.0W

The engine Volvo Penta MD21, 4 cylinder, built in 1980 runs on diesel and the consumption is approx. 4 liters per hour. In my opinion, the cost of the additional consumption is not that important.

We have about 80 to 120 engine hours per year.

[Dacian Todea]

I do not know what the max fuse rating for those panels is but if that is 10A then yes you should be able to parallel all 4 panels.  The thing is that if a panel develops an internal short the other parallel panels will push current in to the defective panel.

So typical large panels have max power point current around 8 to 10A and the panels max fuse rating for those is usually 15A that means only two of those panels can be paralleled as a third one will make so that if one panel is defective the remaining two can push more current in to that defective panel than max size fuse allowed. So with two of those parallel panels you do not need fuse for each panel but if you want 3 of those you need fuse for all 3 panels and 3x MC4 fuses will be more expensive than two DSSR20 thus the reason the DSSR20 was designed for 20A so it can handle two large PV panels with no need for individual fuses.

So is very likely you can parallel all 4 of those panels without needing individual fuses assuming max fuse rating for those panels is 10A or more as the other 3 panels can push no more than 10A typically.

The DSSR20 has no problem handling all 4 panels is just a question of if you need individual fuses for the panels or not.

On top of what the engine normally uses each kWh of energy you get out of the alternator will require an extra liter of fuel. So say you have the engine ON for 100h per year and all that time you use to charge the battery at 12V / 60A (720W) then each hour you will put 0.72kWh in to battery using about 0.72liter of extra fuel compared to not charging just driving or whatever else you do.

So over one year 100h total energy you will put in to battery from alternator will be 72kWh at the cost of around 72 liters of extra fuel so you pay maybe $72 for that energy assuming about $1/liter (may be more or a bit less depending on where you live).

Opposed to that solar PV panels typically have a cost amortisation of $0.02/kWh that is 50x less than cost of charging from alternator. As panels now are $0.5/Watt and they can work for at least 25 years so if you were able to use all energy from them over that lifetime period then cost per kWh will get out to be around $0.02/kWh.

In a sunny day the 200W panels that you have may produce about 1kWh so saving you each day $1 in fuel cost.

While I get that $72/Year will not mean much so it may be irrelevant to you it is still 50x more expensive than solar so I need to mention. Many people think that there is no penalty in fuel consumption from charging the battery if you need to drive anyway so I prefer to make it clear that is not the case.

Here is the link to that 60A renogy https://www.renogy.com/12v-60a-dc-to-dc-battery-charger/  but I think it will be to much for your alternator to handle. Worst case there is a signal that will reduce that current to half so 30A 

You need to consider alternators are just about 50% efficient so for them to output 720W they will need 2x that as input from engine 1440W (about 2hp) and that extra 720W will end up as heat on the alternator and even with a fan you can imagine 720W heater is fairly significant and above what small alternators can handle continuously.